Method and apparatus for user-time-alignment for broadcast works

ABSTRACT

An embodiment of the present invention is a method for broadcasting information from a server to a client which includes the steps of: (a) broadcasting information at predetermined starting times; (b) receiving a request for the information from the client at an arrival time different from the predetermined starting times; and (c) transmitting a time-scale modified version of the information to the client for a period of time.

TECHNICAL FIELD OF THE INVENTION

The present invention pertains to the field of playback of streamingmedia (such as audio and audio-visual works) which are retrieved fromsources having non-deterministic delays such as, for example, servers(such as file servers or streaming media servers) broadcasting data viathe Internet. In particular, the present invention pertains to methodand apparatus for providing playback of audio or audio-visual worksreceived from sources having non-deterministic delays. In furtherparticular, the present invention pertains to method and apparatus forproviding continuous playback of streaming media from sources havingnon-deterministic delays such as, for example, servers (such as fileservers or streaming media servers) broadcasting data via the Internet,an Intranet, or the like.

BACKGROUND OF THE INVENTION

Many digitally encoded audio and audio-visual works are stored as dataon servers (such as file servers or streaming media servers) that areaccessible via the Internet for users to download. FIG. 1 shows, inschematic form, how such audio or audio-visual works are distributedover the Internet. As shown in FIG. 1, media broadcast server 2000accesses data representing the audio or audio-visual work from storagemedium 2100 and broadcasts the data to multiple recipients 2300 ₁ to2300 _(n) across non-deterministic delay network 2200. In this systemthere are two main sources of random delay: (a) delay due to mediabroadcast server 2000 accessing storage medium 2100 and (b) delay due tothe congestion, interference, and other delay mechanisms within network2200.

One well known technique for providing playback of the audio oraudio-visual work is referred to as batch playback. Batch playbackentails downloading an entire work and initiating playback after theentire work has been received. Another well known technique forproviding playback of the audio or audio-visual work is referred to as“streaming.” Streaming entails downloading data which represents theaudio or audio-visual work and initiating playback before the entirework has been received.

There are several disadvantages inherent in both of these techniques. Aprime disadvantage of batch playback is that the viewer/listener mustwait for the entire work to be downloaded before any portion of the workmay be played. This can be tedious since the viewer/listener may wait along time for the transmission to occur, only to discover that the workis of little or no interest soon after playback is initiated. Thestreaming technique alleviates this disadvantage of batch playback byinitiating playback before the entire work has been received. However, adisadvantage of streaming is that playback is often interrupted when theflow of data is interrupted due to network traffic, congestion,transmission errors, and the like. These interruptions are tedious andannoying since they occur randomly and have a random duration. Inaddition, intermittent interruptions often cause the context of theplayback stream to be lost as the viewer/listener waits for playback tobe resumed when new data is received. A further disadvantage ofstreaming is that a user or client is required to poll for additionaldata according to its rate of use of the data. In this manner, a user orclient using data at a rapid rate has to make additional requests fordata at a higher rate than a user or client using the data at a slowerrate.

A further disadvantage in broadcasting audio or audio-visual works usingprior art methods occurs when clients request data asynchronously fromthe media server. Currently, there are two prior art methods forbroadcasting a work to multiple clients requesting data at arbitrarytimes. The first prior art method involves re-broadcasting the work atregular intervals. This prior art method is efficient for the mediaserver since its storage access patterns and load are basicallyindependent of the number of clients receiving the audio or audio-visualwork. A major problem with this prior art method is that clients mustjoin a re-broadcast in the middle of the audio or audio-visual workcurrently being broadcast, or wait for the next re-broadcast to begin toview the start of the audio or audio-visual work.

The second prior art method initiates a re-broadcast of the audio oraudio-visual work each time a client requests to view the audio oraudio-visual work. This prior art method has the advantage that clientdo not have to wait to view the start of work and begin receptionimmediately. A major problem with this second prior art method is thatthe media server must monitor, track and fulfill the request of eachclient requesting data individually. This causes a dramatic increase inserver load during heavy use since multiple requests arrivesimultaneously, and storage access patterns and broadcast load varywidely. As a result, the media server's capacity to serve a number ofclients in a reasonable time is limited.

As one can readily appreciate from the above, a need exists in the artfor a method and apparatus for providing substantially continuousplayback of streaming media such as audio and audio-visual worksreceived from sources having non-deterministic delays such as a fileserver broadcasting data via the Internet. In addition, a need exists inthe art for a method and apparatus for broadcasting streaming media onan efficient basis that maximizes broadcast media server capacity.

SUMMARY OF THE INVENTION

Embodiments of the present invention advantageously satisfy theabove-identified need in the art and provide method and apparatus forbroadcasting streaming media on an efficient basis that maximizesbroadcast media server capacity.

One embodiment of the present invention is a method for broadcastinginformation from a server to a client which comprises the steps of: (a)broadcasting information at predetermined starting times; (b) receivinga request for the information from the client at an arrival timedifferent from the predetermined starting times; and (c) transmitting atime-scale modified version of the information to the client for aperiod of time.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows, in schematic form, how audio or audio-visual works arebroadcast from a server (for example, a file server or a streaming mediaserver) to recipients over a network such as, for example, the Internet;

FIG. 2 shows a block diagram of an embodiment of the present inventionwhich provides substantially continuous playback of an audio oraudio-visual work received from a source having non-deterministic delayssuch as a server (for example, a file server or a streaming mediaserver) broadcasting data via the Internet;

FIG. 3 shows, in pictorial form, low and high thresholds used in oneembodiment of Capture Buffer 400 for the embodiment of the presentinvention shown in FIG. 2;

FIG. 4. shows a graph of playback rate versus amount of data in CaptureBuffer 400 using eqns. (2)-(4) for the embodiment of the presentinvention shown in FIG. 2;

FIG. 5. shows, in graphical form, relative amounts of data at an inputand an output of TSM System 800 in the embodiment of the presentinvention shown in FIG. 2 during time-scale expansion, i.e., slow downof the playback rate of the streaming media;

FIG. 6. shows, in graphical form, relative amounts of data at an inputand an output of TSM System 800 compression in the embodiment of thepresent invention shown in FIG. 2 during time-scale compression, i.e.,speed up of the playback-rate of the streaming media;

FIG. 7 shows a block diagram of media server 3000 which re-broadcasts anaudio or audio-visual work is at regular intervals;

FIG. 8A shows, in graphical form, encoding, transmitting and decodingportions of an audio or audio-visual work;

FIG. 8B shows, in graphical form, a composition and transmission methodutilized by Work Stream 3200 to form and transmit a TDM composite signalto Multicaster 3300 of embodiment 3000 shown in FIG. 7 of embodiment3000;

FIG. 9A shows a graph of location of a segment (offset from an origin)of the audio or audio-visual work being re-broadcast by embodiment 3000shown in FIG. 7 as a function of time;

FIG. 9B shows a graph of work-encoded-data-block number (offset from anorigin) of the audio or audio-visual work being re-broadcast byembodiment 4000 shown in FIG. 10 as function of time;

FIG. 9C shows a graph of position (offset from an origin) of an audio oraudio-visual work being received by a media playback device thatincorporates storage of the audio or audio-visual work, such as, forexample a digital VCR, hard-disk based VCR, and the like;

FIG. 10 shows a block diagram of embodiment 4000 of the presentinvention that transitions asynchronously arriving requests to receive aparticular audio or audio-visual work to synchronous re-broadcasts ofthe audio or audio-visual work;

FIG. 11A shows a graph of location (offset from an origin) of an audioor audio-visual work being re-broadcast by embodiment 5000 shown in FIG.12 as a function of time in accordance with the further aspect of thepresent invention;

FIG. 11B shows, in graphical form, encoding portions of a Time-ScaleModified audio or audio-visual work to form Time-Scale Modified Leaders;

FIG. 12 shows a block diagram of embodiment 5000 of the presentinvention which: (a) transmits Time-Scale Modified Leaders; (b) joinsre-broadcast offset streams of an audio or audio-visual work; and (c)transmits offset streams of an audio or audio-visual work;

FIG. 13 shows a graph of location (offset from an origin) in normal andTime-Scale Modified versions of offset re-broadcasts of an audio oraudio-visual work versus time on the horizontal axis;

FIG. 14 shows a block diagram of embodiment 21000 of the presentinvention which transmits information relating to the playback speedand/or content of media data to clients receiving the media data; and

FIG. 15 shows a block diagram of embodiment 24000 of the presentinvention in which information relating to the playback speed and/orcontent of the media data being broadcast to clients is embedded in themedia work.

DETAILED DESCRIPTION

FIG. 2 shows a block diagram of embodiment 1000 of the present inventionwhich provides substantially continuous playback of an audio oraudio-visual work received from a source having non-deterministic delayssuch as a server (for example, a file server or a streaming mediaserver) broadcasting via the Internet. As shown in FIG. 2, streamingdata source 100 provides data representing an audio or audio-visual workthrough network 200 to User System 300 (US 300), which data is receivedat a non-deterministic rate by US 300. Capture Buffer 400 in US 300receives the data as input. In a preferred embodiment of the presentinvention, Capture Buffer 400 is a FIFO (First In First Out) bufferexisting, for example, in a general purpose memory store of US 300.

In the absence of delays in arrival of data at US 300 from network 200,the amount of data in Capture Buffer 400 ought to remain substantiallyconstant as a data transfer rate is typically chosen to be substantiallyequal to a playback rate. However, as is well known to those of ordinaryskill in the art, pauses and delays in transmission of the data throughnetwork 200 to Capture Buffer 400 cause data depletion therein. Datadepletion in Capture Buffer 400 occurs because, simultaneously, data isinput thereto from network 200 while data is output (for example, at aconstant rate) therefrom to satisfy data use requirements of PlaybackSystem 500. As should be clear to those of ordinary skill in the art, ifdata transmitted to US 300 is delayed long enough, data in CaptureBuffer 400 will be consumed, and Playback System 500 must pause until asufficient amount of data has arrived to enable resumption of playback.Thus, a typical playback system must constantly check for arrival of newdata while the playback system is paused, and it must initiate playbackonce a sufficient amount of new data is received.

In accordance with the present invention, data input to Capture Buffer400 of US 300 is buffered for a predetermined amount of time, whichpredetermined amount of time typically varies, for example, from one (1)second to several seconds. Then, Time-Scale Modification (TSM) methodsare used to slow the playback rate of the audio or audio-visual work tosubstantially match a data drain rate required by Playback System 500with a streaming data rate of the arriving data representing the audioor audio-visual work. As is well known to those of ordinary skill in theart, presently known methods for Time-Scale Modification (“TSM”) enabledigitally recorded audio to be modified so that a perceived articulationrate of spoken passages, i.e., a speaking rate, can be modifieddynamically during playback. During Time-Scale expansion, TSM System 800requires less input data to generate a fixed interval of output data.Thus, in accordance with the present invention, if a delay occurs duringtransmission of the audio or audio-visual work from network 200 to US300 (of course, it should be clear that such delays may result from anynumber of causes such as delays in accessing data from a storage device,delays in transmission of the data from a media server, delays intransmission through network 200, and so forth), the playback rate isautomatically slowed to reduce the amount of data drained from CaptureBuffer 400 per unit time. As a result, and in accordance with thepresent invention, more time is provided for data to arrive at US 300before the data in Capture Buffer 400 is exhausted. Advantageously, thisdelays the onset of data depletion in Capture Buffer 400 which wouldcause Playback System 500 to pause.

As shown in FIG. 2, Capture Buffer 400 receives the following as input:(a) media data input from network 200; (b) requests for informationabout the amount of data stored therein from Capture Buffer Monitor 600;and (c) media stream data requests from TSM System 800. In response,Capture Buffer 400 produces the following as output: (a) a stream ofdata representing portions of an audio or audio-visual work (output toTSM System 800); (b) a stream of location information used to identifythe position in the stream of data (output to TSM System 800); and (c)the amount of data stored therein (output to Capture Buffer Monitor600). It should be well known to those of ordinary skill in the art thatCapture Buffer 400 may include a digital storage device. There are manymethods well known to those of ordinary skill in the art for utilizingdigital storage devices, for example a “hard disk drive,” to store andretrieve general purpose data. There exist many commercially availableapparatus which are well known to those of ordinary skill in the art foruse as a digital storage device such as, for example, a CD-ROM, adigital tape, a magnetic disc.

As further shown in FIG. 2, and in accordance with the presentinvention, TSM Rate Determiner 700 receives the following as input: (a)a signal (from Capture Buffer Monitor 600) that represents the amount ofdata present in Capture Buffer 400; (b) a signal (output, for example,from Playback System 500 or from another module of US 300) thatrepresents a current data consumption rate of Playback System 500; (c) alow threshold value parameter (T_(L) which is described in detail below)for the amount of data in Capture Buffer 400; (d) a high threshold valueparameter (T_(H) which is described in detail below) for the amount ofdata in Capture Buffer 400; (e) a parameter designated Interval_Size;and (f) a parameter designated Speed_Change_Resolution. In response, TSMRate Determiner 700 produces as output a rate signal representing a TSMrate, or playback rate, which can help better balance the dataconsumption rate of Playback System 500 with an arrival rate of data atCapture Buffer 400.

In a preferred embodiment of the present invention, TSM Rate Determiner700 uses the parameter Interval_Size to segment the input digital datastream in Capture Buffer 400 and to determine a single TSM rate for eachsegment of the input digital stream. Note, the length of each segment isgiven by the value of the Interval_Size parameter.

TSM Rate Determiner 700 uses the parameter Speed_Change_Resolution todetermine appropriate TSM rates to pass to TSM System 800. A desired TSMrate is converted to one of the quantized levels in a manner which iswell known to those of ordinary skill in the art. This means that theTSM rate, or playback rate, can change only if the desired TSM ratechanges by an amount that exceeds the difference between quantizedlevels, i.e., Speed_Change_Resolution. As a practical matter then,parameter Speed_Change_Resolution filters small changes in TSM rate, orplayback rate. The parameters Interval_Size and Speed_Change_Resolutioncan be set as predetermined parameters for embodiment 1000 in accordancewith methods which are well known to those of ordinary skill in the artor they can be entered and/or varied by receiving user input through auser interface in accordance with methods which are well known to thoseof ordinary skill in the art. However, the manner in which theseparameters are set and/or varied are not shown for ease of understandingthe present invention.

As still further shown in FIG. 2, TSM System 800 receives as input: (a)a stream of data representing portions of the audio or audio-visual work(output from Capture Buffer 400); (b) a stream of location information(output from Capture Buffer 400) used to identify the position in thestream of data being sent, for example, a sample count or time value;and (c) the rate signal specifying the desired TSM rate, or playbackrate (output from TSM Rate Determiner 700).

In accordance with the present invention, TSM System 800 modifies theinput stream of data in accordance with well known TSM methods toproduce, as output, a stream of samples that represents a Time-ScaleModified signal. The Time-Scale modified output signal contains fewersamples per block of input data if Time-Scale Compression is applied, asshown in FIG. 6. Similarly, if Time-Scale Expansion is applied, theoutput from TSM System 800 contains more samples per block of inputdata, as shown in FIG. 5. Thus, TSM System 800 can create more samplesthan it is given by creating an output stream with a slower playbackrate (Time-Scale Expanded). Similarly, TSM System 800 can create fewersamples than it is given by creating an output stream with a fasterplayback rate (Time-Scale Compressed). In a preferred embodiment of thepresent invention, the TSM method used is a method disclosed in U.S.Pat. No. 5,175,769 ( the '769 patent), which '769 patent is incorporatedby reference herein, the inventor of the present invention also being ajoint inventor of the '769 patent. Thus, the output from TSM System 800is a stream of samples representing portions of the audio oraudio-visual work, which output is applied as input to Playback System500. Playback System 500 plays back the data output from TSM System 800.There are many well known methods of implementing Playback System 500that are well known to those of ordinary skill in the art. For example,many methods are known to those of ordinary skill in the art forimplementing Playback system 500, for example, as a playback engine.

In accordance with the present invention, the stream of digital samplesoutput from TSM System 800 has a playback rate, supplied from TSM RateDeterminer 700, that provides a balance of the data consumption rate ofTSM System 800 with the arrival rate of data input to US 300. Note that,in accordance with this embodiment of the present invention, the dataconsumption rate of Playback System 500 is fixed to be identical to thedata output rate of TSM System 800. Thus, when a playback raterepresenting Time-Scale Expansion is output from TSM Rate Determiner 700and applied as input to TSM System 800, the number of data samplesrequired per unit time by TSM System 800 is reduced in proportion to theamount of Time-Scale Expansion. A reduction in the number of datasignals sent to TSM System 800 slows the data drain-rate from CaptureBuffer 400 and, as a result, less data from Capture Buffer 400 isconsumed per unit time. This, in turn, increases the amount of playbacktime before a pause is required due to emptying of Capture Buffer 400.

As one of ordinary skill in the art should readily appreciate, althoughthe present invention has been described in terms of slowing downplayback, the present invention is not thusly limited and includesembodiments where the playback rate is increased in situations wheredata arrives in Capture Buffer 400 at a rate which is faster than therate at which it would be consumed during playback at a normal rate. Inthis situation, the playback rate is increased and the data is consumedby TSM System 800 at a faster rate to avoid having Capture Buffer 400overflow.

As one of ordinary skill in the art can readily appreciate, wheneverembodiment 1000 provides playback rate adjustments for an audio-visualwork, TSM System 800 speeds up or slows down visual information to matchthe audio in the audio-visual work. To do this in a preferredembodiment, the video signal is “Frame-subsampled” or “Frame-replicated”in accordance with any one of the many methods known to those ofordinary skill in the prior art to maintain synchronism between theaudio and visual portions of the audio-visual work. Thus, if one speedsup the audio and samples are requested at a faster rate, the framestream is subsampled, i.e. frames are skipped.

Although FIG. 2 shows embodiment 1000 to be comprised of separatemodules, in a preferred embodiment, Playback System 500, Capture BufferMonitor 600, TSM Rate Determiner 700, and TSM System 800 are embodied assoftware programs or modules which run on a general purpose computersuch as, for example, a personal computer. It should be well known toone of ordinary skill in the art, in light of the detailed descriptionabove, how to implement these programs or modules in software.

As should be clear to those of ordinary skill in the art, embodiments ofthe present invention include the use of any one of a number ofalgorithms for determining the playback rate to help balance the rate ofdata consumption for playing back the audio or audio-visual works withthe rate of data input from network 200 having non-deterministic delays.In one embodiment of the present invention, the playback rate isdetermined to vary with the fraction of Capture Buffer 400 that isfilled with data. For example, for each 10% decrement of data depletion,the playback rate is reduced by 10%, except when the input data containsan “end” signal. It should be clear to those of ordinary skill in theart how to modify this algorithm to achieve any of a number of desiredbalance conditions. For example, in situations where a delay durationcan vary drastically, a non-linear relationship may be used to determinethe playback rate. One non-linear function that may be used is theinverse tangent function. In this case,Playback Rate=tan h ⁻¹((2*#samples_in_buffer/elements_in_buffer))−1)  (1)where #samples_in_buffer is the number of samples of data in CaptureBuffer 400 and elements_in_buffer is the total number of samples of datathat can be stored in Capture Buffer 400.

In a preferred embodiment of the present invention, a low threshold(T_(L)) value and a high threshold (T_(H)) value are be used toconstruct a piece-wise graph of playback rate versus amount of data inCapture Buffer 400. FIG. 3 shows, in pictorial form, how T_(L) and T_(H)relate to the amount of data in Capture Buffer 400. These thresholds areused in accordance with the following set of equations:For 0<=X<=T _(L) Playback Rate=Scale*tan h ⁻¹((X−T _(L))/T _(L))   (2)For T _(L) <X<T _(H) Playback Rate=1.0 (the default playback rate)   (3)For T _(H) <=X<=Max Playback Rate=Scale*tan h ⁻¹((X−T _(H))/(Max−T_(H)))   (4)where Scale is arbitrary scale factor.

FIG. 4. shows a graph of playback rate versus amount of data in CaptureBuffer 400 using eqns. (2)-(4). From FIG. 4, one can readily appreciatethat for small deviations from an ideal amount of data in Capture Buffer400 (origin 0 in FIG. 4), changes in the playback rate are linear;however, larger deviations generate a more pronounced non-linearresponse. Further, changes in the amount of data in Capture Buffer 400which remain between low threshold level T_(L) and high threshold levelT_(H) do not cause any change in playback rate. The parameters T_(L) andT_(H) can be set as predetermined parameters for embodiment 1000 inaccordance with methods which are well known to those of ordinary skillin the art or they can be entered and/or varied by receiving user inputthrough a user interface in accordance with methods which are well knownto those of ordinary skill in the art. However, the manner in whichthese parameters are set and/or varied are not shown for ease ofunderstanding the present invention.

As should be clear to those of ordinary skill in the art, the inventivetechnique for providing substantially continuous playback may becombined with any number of apparatus which provide time-scalemodification and may be combined with or share components with suchsystems.

It should be clear to those of ordinary skill in the art, in light ofthe detailed description set forth above, that in essence, embodimentsof the present invention (a) determine a measure of a mismatch between adata arrival rate and a data consumption rate and (b) utilize time-scalemodification to adjust these rates. Various embodiments of the inventionutilize various methods (a) for determining information which indicatesthe measure of the mismatch and (b) for determining a playback ratewhich enables time-scale modification to adjust for the mismatch in apredetermined amount.

In light of this, in another embodiment of the present invention, theplayback system determines that there is a data mismatch because itdetermines a diminution in the arrival of data for playback orsubsequent distribution. In response, the playback system sends thisinformation to the TSM Rate Determiner to develop an acceptable playbackrate. For example, the playback rate may be reduced by a predeterminedamount based on an input parameter or in accordance with any one of anumber of algorithms that may be developed by those of ordinary skill inthe art.

Embodiments of the present invention are advantageous in enabling asingle-broadcast system utilizing a broadcast server to provide a singlebroadcast across one or more non-deterministic delay networks tomultiple recipients, for example across the Internet and/or othernetworks such as Local Area Networks (LANs) and Wide Area Networks(WANs). In such a single-broadcast system, the path to each recipientvaries. In fact, the path to each recipient may dynamically change basedon loading, congestion and other factors. Therefore, the amount of delayassociated with the transmission of each data packet that has been sentby the broadcast server varies. In prior art client-server schemes, eachrecipient has to notify the broadcast server of its readiness to receivemore data, thereby forcing the broadcast server to serve multiplerequests to provide a steady stream of data at the recipients' dataports. Advantageously, embodiments of the present invention enable thebroadcast server to send out a steady stream of information, and therecipients of the intermittently arriving data to adjust the playbackrate of the data to accommodate the non-uniform arrival rates. Inaddition, in accordance with the present invention, each of therecipients can accommodate the arrival rates independently.

Another aspect of the present invention advantageously involvessimplification of a transmission protocol used for communication ofstreaming media between a client and, for example, a server such as amedia or broadcast server. In accordance with this additional aspect ofthe present invention, an inventive transmission protocol comprises theclient's sending a data transmission rate to the media or broadcastserver. In response, the server transmits data to the serversubstantially at that rate. In one embodiment of the present invention,the data transmission rate is in the form of a playback rate for a work.In this case, the server adjusts its data transmission rate in a mannerwhich is well known to those of ordinary skill in the art so that theamount of data received by the client substantially matches the client'splayback rate for the work. Thus, for embodiments of this aspect of thepresent invention, the broadcast server need not change its distributionrate unless and until a new request is received from the client. As onecan readily appreciate, the inventive transmission protocol isadvantageous because its use reduces: (a) a network protocol bandwidthrequired for streaming by substantially reducing repeated requests fordata from the client and (b) the number of messages the server mustprocess.

Another aspect of the present invention pertains to media broadcastingwherein media or broadcast servers begin broadcasts of a particular work(for example, the day's news) at regular time intervals, for example,every 5 minutes. In accordance with an embodiment of the presentinvention, a client that sends a request to view or listen to theparticular work is sent a stream of the particular work (substantiallyimmediately) which is closest (in the temporal sense) to the beginningof a broadcast of the particular work (in a manner that will bedescribed in detail below) rather than waiting for a re-broadcast tobegin or joining an in-progress broadcast. After a transition period (tobe described in detail below), the client joins one of the regularbroadcasts and receives data therefrom. Advantageously, in accordancewith the present invention, there is a reduction in client wait time anda reduction in client load for the media or broadcast servers. Althoughembodiments of the present invention are described below in the contextof broadcasting data for ease of understanding the invention, it shouldbe understood that the present invention is not thereby limited. Infact, among other things, embodiments of the present invention can alsobe applied to accessing data as well.

FIG. 7 shows a block diagram of embodiment 3000 of a media server whichre-broadcasts an audio or audio-visual work at regular intervals. Asshown in FIG. 7, Storage Device 3100 is a storage device of a type whichis well known to those of ordinary skill in the art. Storage Device 3100stores a representation (preferably a digital representation, or anyrepresentation that can be converted to a digital representation inaccordance with methods which are well known to those of ordinary skillin the art) of an audio or audio-visual work or data of interest to auser (such as a stream of stock quotes, market data, advertisements, andso forth). Storage Device 3100 receives, as input, data requests fromWork Streamer 3200, and provides, as output, the data requested.

As further shown in FIG. 7, Work Streamer 3200 receives as input: (a) acode (for example, a number) which represents a desired Re-broadcastInterval (“RBI”) (from Re-broadcast Interval Determiner 3700); (b) acode (for example, a number) which represents a desired number ofTime-Division Multiplexed (TDM) channels (from Re-broadcast IntervalDeterminer 3700); (c) a code (for example, a number) which representsthe duration of the audio or audio-visual work being re-broadcast (fromRe-broadcast Interval Determiner 3700); and (d) data from Storage Device3100. Work Streamer 3200 produces, as output, a Time-DivisionMultiplexed composite signal (described in detail below), which outputis applied as input to Multicaster 3300. As will be described in detailbelow, in accordance with the preferred embodiment of the presentinvention, Work Streamer 3200 creates numerous re-broadcasts of theaudio or audio-visual work by sending appropriately interleaved segmentsof the work in the form of the Time-Division Multiplexed signal toMulticaster 3300. Advantageously, in accordance with the preferredembodiment of the present invention, data accesses to Storage Device3100 are organized by Work Streamer 3200 to reduce seek time, decreaselatency, and increase throughput by interleaving and caching accesses todata representing the audio or audio-visual work. It should be clear tothose of ordinary skill in the art that embodiments of this aspect ofthe present invention are not limited to generating the compositeTime-Division Multiplexed signal and include embodiments where the datafor the various re-broadcasts are each generated from a separate signal.

As still further shown in FIG. 7, Re-broadcast Interval Determiner(“RBID”) 3700 receives, as input, (a) a code (for example, a number)which represents the duration of an audio or audio/visual work and (b) acode (for example, a number) that represents the number of re-broadcastoffset channels (to be described in detail below). RBID 3700 produces,as output: (a) a code (for example, a number) which represents a desiredRe-broadcast Interval (“RBI”) (sent to Work Streamer 3200); (b) a code(for example, a number) which represents a desired number ofTime-Division Multiplexed (TDM) channels (sent to Work Streamer 3200);(c) a code (for example, a number) which represents the duration of theaudio or audio-visual work being re-broadcast (sent to Work Streamer3200). In accordance with the present invention, RBID 3700 computes theRBI by applying one of a number of formulas. In the preferred embodimentof the present invention, the following formula is used:RBI=Duration of audio or audio-visual work/No. of re-broadcast offsetchannels   (5)

As yet still further shown in FIG. 7, Multicaster 3300 receives, asinput: (a) a data stream (the Time-Division Multiplexed compositesignal) from Work Streamer 3200 and (b) client information (for example,control and destination) from Request Processor 3500. Multicaster 3300produces, as output, data (for example, message packets) directed towardparticular clients for re-broadcast on a network such as the Internet,WAN, LAN, etc. In accordance with the present invention, Multicaster3300 manages a list of all clients that should receive data fromparticular portions of the TDM composite signal in accordance with anyone of a number of methods which are well known to those of ordinaryskill in the art. Then, whenever the particular portion of data in theTDM composite signal is received from Work Streamer 3200, Multicaster3300 sends the particular portion of data to all clients (recipients) inthe list who are to receive the particular portion of data (also knownas multicasting). Many methods for broadcasting a portion of data from adata stream (for example, a Time-Division Multiplexed composite signal)to multiple recipients are well known to those of ordinary skill in theart. Control information from Request Processor 4500 is used inaccordance with methods that are well known to those of ordinary skillin the art to modify the list of recipients, for example, to add arecipient, or to remove a recipient from the list of destinations whenthe recipient no longer desires to receive data from the server.

As yet again still further shown in FIG. 7, Request Processor 3500receives, as input, requests for data from clients connected via Network3990 (for example, an Internet, WAN, LAN, or the like). In response,Request Processor 3500 produces, as output, information identifying theclient and appropriate re-broadcast control information such as, forexample, “request data that is identified by an appropriate dataidentifier,” “disconnect,” and other messages that are used to obtaindata from embodiment 3000. It should be clear to those of ordinary skillin the art, that such information identifying the client and appropriatere-broadcast control information may be obtained: (a) by dialogs betweenthe client and Request Processor 3500 in accordance any one of manymethods that are well known to those of ordinary skill in the artincluding, without limitation, by use of forms that are contained on webpages that are transmitted to the client over Network 3990 in accordanceany one of the many methods that are well known to those of ordinaryskill in the art.

Although FIG. 7 shows embodiment 3000 to be comprised of separatemodules, in a preferred embodiment, the modules are embodied as softwareprograms or modules which run on a general purpose computer such as, forexample, a personal computer. It should be well known to one of ordinaryskill in the art, in light of the detailed description above, how toimplement these programs or modules in software.

Conversely, components of embodiment 4000 may exist in separatelocations connected to one another by a network or any othercommunication means (where the use of the term means is used in thebroadest sense possible).

In accordance with this embodiment of the present invention, an audio oraudio-visual work is encoded into data that is later decoded to recreatethe original audio or audio-visual work. Those of ordinary skill in theart should readily appreciate that the amount of data that represents aparticular portion of the audio or audio-visual work can be transmitted,re-broadcast, and/or accessed from Storage Device 3100 in a timeinterval that is significantly less than the playback time interval ofthe particular portion. FIG. 8A shows the playback time of segments(Seg0, Seg1, . . . , SegN) of an original audio or audio-visual work,plotted along time axis 3001. The segments are encoded as data inaccordance with methods that are well known to those of ordinary skillin the art, and the transmission times for the encoded data blocks (D0,D1, . . . , DN) which correspond to the segments (Seg0, Seg1, . . . ,SegN) are shown along time-axis 3002. The time of receipt of thetransmitted encoded data blocks (D0, D1, . . . , DN) are plotted alongtime axis 3003. As should be clear to those of ordinary skill in theart, the encoded data blocks (D0, D1, . . . , DN) are received after anarbitrary transmission delay through Network 3990. Lastly, afterdecoding, the segments (Seg0, Seg1, . . . , SegN) of the reconstructedaudio or audio-visual work are plotted along time-axis 3004. Manymethods are well known to those of ordinary skill in the art forencoding and decoding audio or audio-visual works.

Since, as discussed above, the transmission time of data that representsa particular portion of an audio or audio-visual work is generallysmaller than the playback time interval of the particular portion, twoor more audio or audio-visual works can be transmitted across a networkby interleaving or Time-Division Multiplexing (TDM) the datarepresenting the two audio or audio-visual works. Many methods are wellknown to those of ordinary skill in the art for interleaving andTime-Division Multiplexing data representing audio or audio-visual worksduring transmission across a network. In the preferred embodiment of thepresent invention, Time-Division Multiplexing is used to transmit datato Multicaster 3300. In particular, Work Streamer 3200 accesses datafrom Storage Device 3100, and outputs a TDM stream of data toMulticaster 3300.

In accordance with the preferred embodiment of the present invention,the audio or audio-visual work is divided into segments that are encodedas data for efficient storage and transmission. The encoded datarepresenting an interval of the media work will be referred to as a“work-encoded-data-block.” FIG. 8B shows, in graphical form, acomposition and transmission method utilized by Work Stream 3200 to formand transmit a TDM composite signal to Multicaster 3300 of embodiment3000 shown in FIG. 7 of embodiment 3000. As shown in FIG. 8B, time axis3010 shows the playback time of segments (Seg0, Seg1, . . . , Seg5) ofthe audio or audio-visual work being re-broadcast. Seg0 corresponds tothe first segment of the audio or audio-visual work. Thus, time axis3010 corresponds to a re-broadcast of the work that starts at the originof the time axis (hence its designation as offset 0). Below time axis3010 is shown the TDM transmit interval of a work-encoded-data-blockthat corresponds to the segment below which it appears (i.e., the timeit takes to transmit the data). As discussed above, the time to transmitthe corresponding work-encoded-data-block is less than the playback timeof the segment. As further shown in FIG. 8B, time axis 3020 shows theplayback time of segments (Seg5, Seg0, . . . , Seg4) of the audio oraudio-visual work being re-broadcast. Seg0 corresponds to the firstsegment of the audio or audio-visual work. Thus, time axis 3020corresponds to a re-broadcast of the work that starts offset from theorigin of the time axis by one Re-broadcast Interval (“RBI”) (hence itsdesignation as offset 1). Below time axis 3020 is shown the TDM transmitinterval of a work-encoded-data-block which corresponds to the segmentbelow which it appears (i.e., the time it takes to transmit the data).However, it is offset in time by an amount equal to the time it takes totransmit the work-encoded-data-block corresponding to segment SEG0 fromthe offset 0 data stream.

Thus, in accordance with the present invention, the re-broadcasts of theaudio or audio-visual work are labeled: offset 0 stream, offset 1stream, offset 2 stream, and so forth (along time axes 3010-3060) andthe various offset streams represent re-broadcasts of the audio oraudio-visual work at regular time intervals, which are referred to asRe-broadcast Intervals (“RBI”). That is, the starting times for theparticular audio or audio-visual work being re-broadcast are offset atregular intervals, RBI, with the start of the re-broadcast of the audioor audio-visual work being denoted by Seg0 in each of the offset datastreams shown in FIG. 8B).

In accordance with the preferred embodiment of the present invention,Work Streamer 3200 transmits composite signal 3065 (as Shown in FIG. 8B)to Multicaster 3500. As shown in FIG. 8B, composite signal 3065 is a TDMsignal that is made up of TDM frames (this type of Time-DivisionMultiplexing is well known to those of ordinary skill in the art andmany methods are well known to those of ordinary skill in the art forforming such a signal). As further shown in FIG. 8B, each TDM frame ofcomposite signal 3065 comprises a work-encoded-data-block from each ofthe offset streams 0-5, wherein each of the work-encoded-data-blocks isoffset in time for the time it takes to transmit awork-encoded-data-block. As one can readily appreciate, each TDM framethereby comprises a work-encoded-data-block from each of there-broadcasts in the appropriate time slot within the TDM frame. Asshould be well understood by those of ordinary skill in the art, thework-encoded-data-blocks are created by Work Streamer 3200 at theappropriate TDM transmit interval (as indicated on FIG. 8B) by sendingappropriate signals to Storage Device 3100 at regular intervals. Notethat the TDM transmission interval for each of re-broadcast offsetstreams 0-5 occurs at a unique time offset from the start of the TDMFrame. Advantageously, this enables multiple re-broadcasts of the audioor audio-visual work to be sent Multicaster 3300 in a TDM format.Further in accordance with the preferred embodiment of the presentinvention, the use of a TDM composite signal enables interleaved dataaccess to Storage Device 3100 to provide greater performance in manystorage devices of the type that are well known to those of ordinaryskill in the art. It should also be noted that, even though it has beendepicted in this manner for sake of ease of understanding the presentinvention in FIG. 8B, the transmission time required to send awork-encoded-data-block during a particular time slot may not consumethe entire time slot interval.

It should be understood that although the preferred embodiment of thepresent invention utilizes a TDM composite signal, the invention is notthereby restricted and includes embodiments wherein other methodsutilizing multiple streams and/or multiple storage devices, for example,one stream and perhaps one storage device for each re-broadcast, can beemployed to send data from Work Streamer 3200 to Multicaster 3300. Itshould be clear that the TDM composite signal can have a number ofchannels that is bounded by the ability of the system to broadcast toclients without the clients noticing a lapse in transmission (of coursethis cannot account for nondeterministic delays in the network). If alarger number of channels is needed to handle the predeterminedbroadcasts than can be handled by the system without lapses, one could,for example, create multiple TDM composite signals to handle the extraload.

FIG. 9A shows a graph of location of a segment (offset from an origin)of the audio or audio-visual work being re-broadcast by embodiment 3000shown in FIG. 7 as a function of time. As shown in FIG. 9A, duringtransmission of data at normal playback rates, the locations of segmentsof the audio or audio-visual work being broadcast as a function of timeform a line having slope which represents the playback rate (a “normal”playback rate corresponding to a slope of 1) and an intercept on thetime axis at the re-broadcast start time of the particular re-broadcastof the audio or audio-visual work. Data streams 3110-3140 shown in FIG.9A have the same playback rates (and therefore the same slope), but areoffset from one another since they have different re-broadcast starttimes. Note that at any particular time along the horizontal time axismultiple segments from different portions of the audio or audio-visualwork are being re-broadcast simultaneously. This is seen by drawing avertical line that intersects the horizontal time axis at a particulartime.

As further shown in FIG. 9A, at 2 time units from the start of there-broadcast of data stream 3110 (offset 0 data stream), client A0 sendsa request to embodiment 3000 to begin-viewing the particular audio oraudio-visual work being re-broadcast. Client A0 must wait for the nextre-broadcast to begin before receiving data (as shown in FIG. 9A, thenext re-broadcast starts at the temporal location denoted by RBI). Thus,client A0 must wait 8 time units before receiving media or other datarequested from data stream 3120 (offset 1 data stream). Similarly, ifclient A1 sends a request to begin viewing the particular audio oraudio-visual work being re-broadcast 7 time units after the start of there-broadcast of data stream 3110 (offset 0 data stream), client A1 hasto wait 3 time units before receiving media or other data requested fromdata stream 3120 (offset 1 data stream).

FIG. 10 shows a block diagram of embodiment 4000 of the presentinvention that transitions asynchronously arriving requests to receive aparticular audio or audio-visual work to synchronous re-broadcasts ofthe audio or audio-visual work. First, for ease of understanding thepresent invention, a general description of how embodiment 4000 operatesis given with reference to FIG. 9A. In accordance with the presentinvention, embodiment 4000 causes the client to be joined to a datastream whose re-broadcast start time is closest (temporally) to thearrival of the client's request. Thus, in accordance with the presentinvention, for client A0, embodiment 4000 determines that the arrivaltime of the request to begin viewing is closest to the re-broadcaststart time of data stream 3110 (note that the re-broadcast time of datastream 3110 has already occurred). Embodiment 4000 then beginsre-broadcasting data to client A0 at 5/3 the normal rate, i.e., at anaccelerated rate. In accordance with the present invention, transmissionat the accelerated rate enables client A0 to “catch up” to the normalre-broadcast location in the audio or audio-visual work 5 time unitsafter the re-broadcast start time of data stream 3110. In response toreceiving data at the accelerated rate, the client (or the client'sserver) automatically initiates playback at an appropriate rate to keepits arrival or capture buffer from overflowing, for example, inaccordance with aspects of the present invention that have beendescribed in detail above. In an alternative embodiment of the presentinvention, instead of having the client determine the accelerated raterequired by its playback system to avoid an overflow of the datareceived, the accelerated rate is transmitted to the client byembodiment 4000 when transmission is starts.

Next, in accordance with the present invention, whenever embodiment 4000determines that the stream of data being re-broadcast to client A0relates to the same playback position as data stream 3110, embodiment4000 sends client A0 data at the normal rate from data stream 3110.Advantageously, in accordance with the present invention, overhead onembodiment 3000, and the corresponding components of embodiment 4000, isreduced since, as will be explained in detail below, the client nowreceives data from Multicaster 4300 and no additional accesses toStorage Device 4100 or Work Streamer 4200 are required to provide datato the client. Additionally, as will be described in detail below, oncethe transition to the offset stream has occurred, the client no longerconsumes resources Variable Rate Broadcaster 4600.

In a similar manner to that described above, in accordance with thepresent invention, for client A1, embodiment 4000 determines that thearrival time of the request to begin viewing is closest to there-broadcast start of data stream 3120 (note that the re-broadcast timeof data stream 3120 has yet to occur). Embodiment 4000 then beginsre-broadcasting data to client A1 at ⅝ the normal rate, i.e., at areduced rate. In accordance with the present invention, transmission atthe reduced rate enables client Al to reach the normal re-broadcastlocation in the audio or audio-visual work 5 time units after there-broadcast start time of data stream 3120. In response to receivingdata at the reduced rate, the client (or the client's server)automatically initiates playback at an appropriate rate to keep itsarrival or capture buffer from emptying, for example, in accordance withaspects of the present invention that have been described in detailabove. In an alternative embodiment of the present invention, instead ofhaving the client determine the reduced rate required by its playbacksystem to avoid emptying, the reduced rate is transmitted to the clientby embodiment 4000 when transmission is started.

Next, in accordance with the present invention, whenever system 4000determines that the stream of data being re-broadcast to client A1relates to the same playback position as data stream 3120, embodiment4000 sends client A1 data at the normal rate from stream 3120.Advantageously, in accordance with the present invention, overhead onembodiment 3000, and the corresponding components of embodiment 4000, isreduced since, as will be explained in detail below, the client nowreceives data from Multicaster 4300 and no additional accesses toStorage Device 4100 or Work Streamer 4200 are required to provide datato the client. Additionally, as will be described in detail below, oncethe transition to the offset stream has occurred, the client no longerconsumes resources Variable Rate Broadcaster 4600.

We now return to a detailed description of embodiment 4000. As shown inFIG. 10, Storage Device 4100 is a storage device of a type which is wellknown to those of ordinary skill in the art. Storage Device 4100 storesa representation (preferably a digital representation or anyrepresentation that can be converted to a digital representation inaccordance with methods which are well known to those of ordinary skillin the art) of an audio or audio-visual work or data of interest to auser (such as a stream of stock quotes, market data, advertisements, andso forth). Storage Device 4100 receives, as input: (a) data requestsfrom Work Streamer 4200; data requests from Variable Rate Broadcaster4600. Storage Device 4100 provides, as output, the data requested.

As further shown in FIG. 10, Work Streamer 4200 receives as input: (a) acode (for example, a number) which represents a desired Re-broadcastInterval (“RBI”) from Re-broadcast Interval Determiner 4700; (b) a code(for example, a number) which represents a desired number ofTime-Division Multiplexed (TDM) channels; (c) a code (for example, anumber) which represents the duration of the audio or audio visual workbeing re-broadcast; and (d) data transmitted from Storage Device 4100.Work Streamer 4200 produces, as output: (a) a Time-Division Multiplexedcomposite signal as described above (this is applied as input toMulticaster 4300) and (b) a stream of information that provides theplayback position and time offset of each time-offset re-broadcaststream of the work (this is applied as input to Slope/Rate Determiner4400).

As still further shown in FIG. 10, Re-broadcast Interval Determiner(“RBID”) 4700 receives, as input, (a) a code (for example, a number)which represents the duration of an audio or audio/visual work beingre-broadcast and (b) a code (for example, a number) that represents thenumber of re-broadcast offset channels, and produces, as output, datarepresenting the duration of the re-broadcast interval. (“RBI”). Inaccordance with the present invention, Re-broadcast Interval Determiner4700 computes the RBI by applying one of a number of formulas. In thepreferred embodiment of the present invention, the following formula isused:RBI=Duration of audio or audio-visual work/No. of re-broadcast offsetchannels   (6)

As yet still further shown in FIG. 10, Slope Rate Determiner (“SRD”)4400 receives as input: (a) data representing start times for eachoffset data stream of the audio or audio visual work being re-broadcastfrom Work Streamer 4200; (b) arrival times and client identificationinformation from Request Processor 4500; and (c) a set of parametersrepresenting maximum allowable Time-Scale Modification rates (orslopes). SRD 4400 produces as output: (a) client identificationinformation for the client requesting the data (applied as input toVariable Rate Broadcaster 4600 “VRB 4600” and Multicaster 4300); (b) anidentification of the re-broadcast offset data stream the client will besynchronized or merged with (applied as input to VRB 4600); (c) anindication of the time it will take before the synchronization or mergetakes place (“duration to intercept”) (applied as input to VRB 4600 andMulticaster 4300); and (d) a slope, which represents the playback rate(this slope or playback rate is applied as input to VRB 4600). Inaccordance with the present invention, SRD 4400 determines there-broadcast offset data stream whose start time is temporally closestto the arrival time of the client's request by computing the distanceforward and backward in time to the previous offset stream start timeand the next offset stream start time (with respect to the arrivaltime), and choosing the smaller of the forward and backward times. Next,SRD 4400 computes a client playback slope that is greater than 1.0 if“catching-up” to a future playback intercept position in an offsetstream already started, or a client playback slope that is less than 1.0to “slow-down” to a future playback intercept position in an offsetstream which will start in the future. The actual slope can bedetermined by a number of factors such as the utilization of VRB 4600(if a higher slope is used, there is a greater load since data must besent faster), and the maximum allowable Time-Scale Modification rate. Inmost cases slope values will be between ½ and 2.0, and can becalculated: (a) by computing a desired playback position change per unittime; (b) by accessing a pre-computed look-up table; or (c) any othermethod of choosing a reasonable slope, such as, by client input relatingto the speed of the “catch-up.” The “duration to intercept” iscalculated by subtracting the time that data transmission to the clientis initiated from the time interval at which the playback positions ofVRB 4600 and the target offset stream are identical. The “duration tointercept” information is used to signal VRB 4600 when it must endtransmission to the client and to signal Multicaster 4300 when it mustinitiate transmission of the appropriate offset stream.

As yet again still further shown in FIG. 10, VRB 4600 receives as input:(a) data from Storage Device 4100; (b) a slope or playback rate from SRD4400; (c) client identification information for the client requestingthe data from SRD 4400; (d) an identification of the re-broadcast offsetdata stream the client will be synchronized or merged with; and (e)“duration to intercept” from SRD 4400. VRB 4600 obtains the specifieddata received from Storage Device 4100 and broadcasts it to theidentified client at the specified rate for an amount of time equal tothe “duration to intercept” and then stops sending data for that client.VRB 4600 produces as output a stream of data sent to the identifiedclient via a network such as the Internet or Intranet and so forth.

As yet still further shown in FIG. 10, Multicaster 4300 receives asinput: (a) a data stream (the Time-Division Multiplexed compositesignal) from Work Streamer 4200; (b) client information (control anddestination) from Request processor 4500; (c) client identificationinformation for the client requesting the data from SRD 4400; and (d)“duration to intercept” information from SRD 4400. Multicaster 4300produces, as output, data (for example, message packets) directed towardparticular clients for clients for re-broadcast on a network such as theInternet, WAN, LAN, etc. In accordance with the present invention,Multicaster 4300 manages a list of all clients that should receive datafrom particular portions of the TDM composite signal in accordance withany one of a number of methods which are well known to those of ordinaryskill in the art. Then, whenever the particular portion of data in theTDM composite signal is received from Work Streamer 4200, Multicaster4300 sends the particular portion of data to all clients (recipients) inthe list who are to receive the particular portion of data (also knownas multicasting). Many methods for broadcasting a portion of data from adata stream (for example, a Time-Division Multiplexed composite signal)to multiple recipients are well known to those of ordinary skill in theart. Control information from Request Processor 4500 are used inaccordance with methods that are well known to those of ordinary skillin the art to modify the list of recipients, for example, to add arecipient, or to remove a recipient from the list of destinations whenthe recipient no longer desires to receive data from the server. The“duration to intercept” and client information from SRD 4400 is used tonotify Multicaster 4300 when clients previously receiving data from VRB4600 should begin receiving data from one of the offset streams.

Lastly, Request Processor 4500 receives, as input, requests for datafrom clients connected via a network (for example, an Internet, WAN,LAN, or the like). In response, Request Processor 4500 produces, asoutput, information identifying the client and the appropriatere-broadcast control information such as, for example, “request datathat is identified by an appropriate data identifier,” “disconnect,” andother messages that are used to obtain data from embodiment 4000. Itshould be clear to those of ordinary skill in the art, that suchinformation identifying the client and appropriate re-broadcast controlinformation may be obtained: (a) by dialogs between the client andRequest Processor 4500 in accordance any one of many methods that arewell known to those of ordinary skill in the art including, withoutlimitation, by use of forms that are contained on web pages that aretransmitted to the client over a network in accordance any one of themany methods that are well known to those of ordinary skill in the art.

Although FIG. 10 shows embodiment 4000 to be comprised of separatemodules, in a preferred embodiment, the modules are embodied as softwareprograms or modules which run on a general purpose computer such as, forexample, a personal computer. It should be well known to one of ordinaryskill in the art, in light of the detailed description above, how toimplement these programs or modules in software.

Conversely, components of embodiment 4000 may exist in separatelocations connected to one another by a network or any othercommunication means (where the use of the term means is used in thebroadest sense possible).

To better understand the operation of embodiment 4000 described above,FIG. 9B shows a graph of work-encoded-data-block number (offset from anorigin) of the audio or audio-visual work being re-broadcast byembodiment 4000 as function of time. As shown in FIG. 9B, duringtransmission of data at normal playback rates, thework-encoded-data-blocks of the audio or audio-visual work beingre-broadcast as a function of time, form a line having slope 1 and anintercept on the time axis at the re-broadcast start time of theparticular broadcast of the work. As further shown in FIG. 9B, datastreams 3110 and 3120 are offset from one another, i.e., they are datastreams having different “re-broadcast start-times.” However, datastreams 3110 and 3120 have the same playback rate, i.e., the same slopein FIG. 9B, but different intercepts on the time axis corresponding totheir different start times. As discussed above, streams transmitted ata normal rate have slope 1.

As further shown in FIG. 9B, the work-encoded-data-blocks sent by VRB4600 of embodiment 4000 are identical to the work-encoded-data-blockssent by Multicaster 4300 of embodiment 4000, but are simply broadcastwith a different time interval between the work-encoded-data-blocks.This means that VRB 4600 sends the same work-encoded-data-blocks thatMulticaster 4300 sends, but adjusts the time interval betweentransmissions of the work-encoded-data-blocks in order to “catch-up to”or “wait-for” the stream of data blocks sent by Multicaster 4300. If theclient request is received between (n)RBI and (n+½)RBI (less than thehalf-way point, in time, between the nth and the (n+1)st re-broadcaststart time), the inter-transmission interval is shortened to catch-up toan intersection point in the previous offset stream (note the datatransmitted for path 3111 has the same work-encoded-data-blocks as path3110, but spaced closer together in time). If the client request isreceived between (n+½)RBI and (n+1)RBI (more than the half-way point, intime, between the nth and the (n+1)st re-broadcast start time), theinter-transmission interval is lengthened to wait for an intersectionpoint with the next offset stream (note the data transmitted for path3121 has the same work-encoded-data-blocks as path 3120, but spacedfurther apart in time). Note that, in accordance with the presentinvention, only the initial portion of the audio or audio-visual work isbroadcast by VRB 4600, and thus VRB 4600 can cache thework-encoded-data-blocks from the initial portion of the work to furtherreduce the number of accesses to Storage Device 4100. There are manymethods and apparatus that are well known to those of ordinary skill inthe art for caching data, such as, for example, SRAM, DRAM, or smallcapacity hard disks.

Then, in accordance with the present invention, once embodiment 4000 (orthe transmitting server) determines that the stream of data beingbroadcast to client A1 is accessing the same playback position duringthe same time interval as stream 3120, the server sends the client dataat the normal rate from stream 3120 and the overhead on the media serveris reduced. In the preferred embodiment the duration to intercept isused to identify the time at which the stream from VRB 4600 andMulticaster 4300 will intercept and when the responsibility oftransmitting data to the client should transition from VRB 4600 toMulticaster 4300.

Although aspects of the present invention have been described in thecontext of aligning or synchronizing to one of several, offset,re-broadcast data streams, it should be clear that the present inventionis not limited to time alignment of re-broadcasted works. In fact,embodiments of the present invention may also be used to align orsynchronize with (catch up), for example, live broadcasts by storing ortime shifting an audio or audio-visual work that is broadcast only once.For example, in digital VCRs or televisions that contain digital storagefor spooling live broadcasts, a user may watch a live broadcast andinvoke a “Pause” function (by, for example, pressing a “pause andrecord” button) to stop playback and initiate recording of the one-timebroadcast audio or audio-visual work. In response, the one-timebroadcast audio or audio-visual work is recorded from the point wherethe Pause function was invoked to the end of the audio or audio-visualwork. As should be clear, this enables a user to turn to other tasks.After the user is ready to return to the work, playback is resumed atthe location where the “Pause” was initiated by playing the recordedcopy of the one-time broadcast. This playback is said to be“time-shifted” since the playback time differs from the one-timebroadcast time. In prior art devices, there is no mechanism to catch upto the one-time broadcast without deleting or skipping some portion ofthe time-shifted copy of the audio and/or audio-visual work in thebroadcast. However, embodiments of the present invention, can be used tocatch-up to the live one-time broadcast by computing the playback raterequired to catch-up in a predetermined interval, such as a commercialbreak, program boundary, or the like. In this manner users watching atime-shifted version can “catch-up” to a live broadcast after they havepaused their viewing devices.

FIG. 9C shows a graph of position (offset from an origin) of an audio oraudio-visual work being received by a media playback device thatincorporates storage of the audio or audio-visual work, such as, forexample a digital VCR, hard-disk based VCR, and the like. As shown inFIG. 9C, a one-time live broadcast (4001) is being viewed as it isbroadcast. At time Tp, the user invokes the Pause function. Aspreviously described, the one-time live broadcast is recorded afterinvoking the Pause function. At time Tr, the user resumes viewing at thesame location in the work where the Pause function was invoked. However,the user is behind the live broadcast. Using the inventive method andapparatus previously described with respect to embodiment 4000, the userspecifies the amount of time desired to transition back to the one-timelive broadcast (received by Request Processor 4500), and apparatus,similar to Slope/Rate Determiner 4400, computes a Time-ScaleModification Rate, or Playback Rate, that will transition the user tothe one-time live broadcast during the specified interval. The interceptinterval computed by embodiment 4000 determines the time at which themedia playback device may discontinue recording of the one-time livebroadcast, since after the intercept interval, the user will be viewingthe one-time live broadcast as it is received. As shown in FIG. 9C, timeTv marks the time at which the user will again be viewing the livebroadcast. The time interval from Tr to Tv defines the transition periodduring which the user will be watching a Time-Scale compressed (orspeeded-up) version of the recorded material. The time interval from Tpto Tv defines the interval of the one-time live broadcast which must berecorded in order to provide a seamless transition to the live-broadcastfrom a time-shifted viewing reference.

Note that upon intersecting with the one-time live broadcast, there isno longer a need to continue recording the work, and this process isstopped. The ability of embodiment 4000 to merge with or “catch-up” to aone-time live broadcast of a work from a time-shifted copy of the workthat has been recorded significantly reduces the amount of the workwhich must be stored or recorded. This reduction further reduces therequired storage resources required.

In accordance with a further aspect of the present invention, systemoverhead for serving requests from clients that arrive during intervalsbetween the start of re-broadcasts of a particular audio or audio-visualwork is further reduced. In accordance with this further aspect of thepresent invention, portions of the audio or audio-visual work beingbroadcast are Time-Scale Modified at two rates: one rate is faster thannormal speed and one rate is slower than normal speed. These slow-rateand fast-rate broadcast portions of the audio or audio-visual work arere-broadcast during an interval from the start of re-broadcast of thework to a point X during the broadcasting of the work, which point X isa function of the re-broadcast interval and the amount of Time-ScaleModification performed. These portions will be referred to asTime-Scaled Leaders. FIG. 11A shows a graph of location (offset from anorigin) of an audio or audio-visual work being re-broadcast byembodiment 5000 shown in FIG. 12 as a function of time in accordancewith the further aspect of the present invention. As shown in FIG. 11A,embodiment 5000 (TSM System 5400 of embodiment 5000 shown in FIG. 12)time compresses the first 10 time units of the audio or audio-visualwork and creates a new data stream 3210 which has duration 5 units and aplayback rate of 2. Note that only 10 time units of the beginning of theoriginal audio or audio-visual work are time-scale compressed. Next, asshown in FIG. 11A, embodiment 5000 (TSM System 5400 of embodiment 5000shown in FIG. 12) time-expands the first 5 time units of the work andcreates a new data stream 3220 which has duration 10 units and playbackrate of ½. Note that only 5 time units of the beginning of the originalaudio or audio-visual work are time-scale expanded. As further shown inFIG. 11A, playback of either of these two data segments 3210 and 3220may begin at the midpoint of the interval between re-broadcast starttimes (RBI/2), and, upon reaching the end of each Time-Scale Modifieddata stream, the client will be at the same segment location of theaudio or audio-visual work being re-broadcast on an earlier or lateroffset data stream, respectively. In the preferred embodiment, segments(labeled 3211, 3212) of the single time-scale compressed leader 3210 areused to merge with the previous offset stream from starting timesbetween (n)RBI and (n)(RBI/2) as shown in FIG. 11A. Similarly, segments(labeled 3221, 3222) of the single time-scale expanded leader 3220 areused to merge with the next offset stream from starting times between(n)(RBI/2) and RBI(n+1) as shown in FIG. 11A.

As is readily apparent from FIG. 11A, in accordance with the presentinvention, further, smaller time-scale compressed and time-scaleexpanded portions of the audio or audio-visual work are re-broadcastfrom times between the midpoint of the re-broadcast interval, and mergewith the offset streams. In the preferred embodiment segments of thetime-scale compressed leader and segments of the time-scale expandedleader are broadcast from starting times other than the offset streamstart-times and merge with the offset streams. The interval betweenre-broadcasts of the Time-Scale Modified Leaders is Leader Re-broadcastInterval (LRBI), which LRBI can be selected by embodiment 5000. Inaccordance with a preferred embodiment of the present invention, asshown in FIG. 11A, re-broadcasts of the time-scale compressed leader andtime-scale expanded leader may be accomplished utilizing the techniqueof Time-Division Multiplexing for further efficiency.

Advantageously, in accordance with this aspect of the present invention,there is no need to compute playback rates, and a media server needsonly: (a) to select a Time-Scale Modified Leader to send to the clientand (b) to manage a transition from the Time-Scale Modified Leader to adata stream being transmitted at normal speed when appropriate. Thus, inaccordance with this aspect of the present invention, SRD 4400 and VRB4600 of embodiment 4000 are replaced with a Time-Scaled Leader DurationDeterminer, Time-Scale Modification apparatus, and apparatus forstreaming and multicasting the Time-Scale Modified Leaders. Inaccordance with the preferred embodiment of the present invention, theTime-Scale Modified Leaders are re-broadcast at regular intervalsseparated in time by an amount LRBI.

Although the inventive technique has been described using two time-scalemodified leaders and segments thereof, the invention is not thuslylimited and embodiments using leaders with unique TSM rates (playbackrates) are possible. In addition, multiple TSM leaders with differentstart times and different TSM rates may share a common intercept pointin the work.

FIG. 11B shows, in graphical form, encoding portions of a Time-ScaleModified audio or audio-visual work to form Time-Scale Modified Leaders.Playback time of segments (Seg0, Seg1, . . . , SegN) of an originalaudio or audio visual work are plotted along time axis 4037. Thesesegments are encoded as data in accordance with methods that are wellknown to those of ordinary skill in the are, and the transmission timesfor work-encoded-data-blocks (D0, D1, . . . , DN) which correspond tothe segments (Seg0, Seg1, . . . , SegN) are shown along time axis 4039.Playback time of segments (Seg0, Seg1, . . . , SegN) for a time-scalecompressed leader (compresses by a factor of 2) are shown alongtime-axis 4041. These segments are encoded as data, and the transmissiontimes for work-encoded-data-blocks (D0, D1, . . . , DN) which correspondto the segments (Seg0-Seg1, Seg2-Seg3, . . . ) are shown along time axis4043. Lastly, playback time of segments (Seg0, Seg1, . . . , SegN) for atime-scale expanded leader (expanded by a factor of 2) are shown alongtime-axis 4045. These segments are encoded as data, and the transmissiontimes for work-encoded-data-blocks (D0, D1, . . . , DN) which correspondto the segments (Seg0/2, Seg0/2, Seg1/2, Seg1/2 . . . ) are shown alongtime axis 4047.

FIG. 12 shows a block diagram of embodiment 5000 of the presentinvention which: (a) transmits Time-Scale Modified Leaders; (b) joinsre-broadcast offset streams of an audio or audio-visual work; and (c)transmits offset streams of an audio or audio-visual work. As shown inFIG. 12, Re-broadcast Interval Determiner (RBID) 5700 receives, asinput: (a) a code (for example, a number) which represents the durationof an audio or audio-visual work being re-broadcast and (b) a code (forexample, a number) that represents the number of re-broadcast offsetchannels. RBID 5700 produces, as output, data representing the durationof the re-broadcast interval (“RBI”). The RBI is applied as input toWork Streamer 5200, Leader Re-broadcast Interval Determiner 5710, andTime-Scaled Leader Duration Determiner (“TSLDD”) 5600. In accordancewith the present invention, RBID 5700 computes the RBI by applying oneof a number of formulas. In the preferred embodiment, the followingformula is used:RBI=Duration of audio or audio-visual work/No. of re-broadcast offsetchannels   (7)

Work Streamer 5200 and Multicaster 5300 are identical to Work Streamer4200 and Multicaster 4300, respectively, which were described above withrespect to embodiment 4000 shown in FIG. 10.

As further shown in FIG. 12, TSLDD 5600 receives as input: (a) RBI (fromRBID 5700); (b) a user defined parameter representing the time-scalecompression (or speed-up) rate to use; and (c) a user defined parameterrepresenting the time-scale expansion (or slow-down) rate to use. Inresponse, TSLDD 5600 produces, as output, the maximum time interval ofthe input audio or audio-visual work that will be required for creationof time-scale-compressed leaders and time-scale expanded leaders(applied as input to TSM System 5400). TSLDD 5600 computes the timeinterval of the original audio or audio-visual work that will betime-scale compressed to form a time-scale compressed leader and thetime interval of the original audio or audio-visual work that will betime-scale expanded to form a time-scale expanded leader by applying thefollowing formulas:

Speed-Up:Tdo=(I/2)(Speed/(Speed−1))   (8)where: Tdo=Time Interval of the original audio or audio-visual work tobe time-scale compressed; Speed=speed-up factor(i.e. >1)=1/time-compression factor; and I=Re-broadcast interval.Slow-Down:Tdo=(I/2)(Speed/(1−Speed))   (9)where: Tdo=Time Interval of the original audio or audio-visual work tobe time-scale expanded; Speed=slow-down factor (i.e.<1)=1/time-expansion factor; and I=Re-broadcast interval.

As one can readily appreciate from the above, for speed-up by a factorof 2 (i.e., time-compression by ½) and slow-down by a factor of ½ (i.e.,time-expansion by 2), the time-compressed leader is obtained from asegment of the original audio or audio-visual work which starts at thebeginning of the audio or audio-visual work and has a time intervalequal to the re-broadcast interval. The time-expanded leader is obtainedfrom a segment of the original audio or audio-visual work which startsat the beginning of the audio or audio-visual work and has a timeinterval equal to ½ the re-broadcast interval. This can also beunderstood as described above with respect to FIG. 11A.

As shown in FIG. 12, Time-Scale Modification System (TSMS) 5400 receivesas input: (a) data from Storage Device 5100 representing the originalaudio or audio-visual work; (b) the time interval of the original audioor audio-visual work required to generate time-scale compressed leaders(from TSLDD 5600); (c) the time interval of the original audio oraudio-visual work required to generate a time-scale expanded leaders(from TSLDD 5600); (d) the speed factor for time-scale compression (fromTSLDD 5600); and (e) the speed factor for time-scale expansion (fromTSLDD 5600). TSMS 5400 produces as output (a) a time-scale compressedleader; and (b) a time-scale expanded leader. TSMS 5400 time-scalecompresses (at the specified speed factor) the specified duration of theoriginal work to produce the time-scale compressed leader. Similarly,TSMS 5400 time-scale expands (at the specified speed factor) thespecified duration of the original work to produce the time-scaleexpanded leader. In a preferred embodiment of the present invention, thetime-scale-compressed leader and the time-scale expanded leader arestored in Storage Device 5100.

Storage Device 5100 is a storage device of a type which is well known tothose of ordinary skill in the art. Storage Device 5100 stores arepresentation (preferably a digital representation or anyrepresentation that can be converted to a digital representation inaccordance with methods which are well known to those of ordinary skillin the art) of an audio or audio-visual work or data of interest to auser (such as a stream of stock quotes, market data, advertisements, andso forth) and Time-Scale Modified Leaders.

As shown in FIG. 12, Request Processor (RP) 5500 receives, as input,requests for data from clients connected via a network (for example, anInternet, WAN, LAN, or the like). In response, Request Processor 5500produces, as output, information identifying the client and theappropriate re-broadcast control information such as, for example,“request for data that is identified by an appropriate data identifier,”“disconnect,” and other messages that are used to obtain data fromembodiment 5000. It should be clear to those of ordinary skill in theart, that such information identifying the client and appropriatere-broadcast control information may be obtained: (a) by dialogs betweenthe client and Request Processor 4500 in accordance any one of manymethods that are well known to those of ordinary skill in the artincluding, without limitation, by use of forms that are contained on webpages that are transmitted to the client over a network in accordanceany one of the many methods that are well known to those of ordinaryskill in the art. Output from RP 5500 is applied as input to StreamAssignment System (SAS) 5550.

As shown in FIG. 12, SAS 5550 receives, as input: (a) information fromRP 5500; (b) leader-offset-stream information (described in detailbelow) from TSCL Streamer 5210; (c) leader-offset-stream information(described in detail below) from TSEL Streamer 5220; and (d) information(described in detail below) from LRBID 5710. SAS 5550 produces, asoutput, control information which is received by Multicaster 5300, TSCLMulticaster 5310, and TSEL Multicaster 5320. In accordance with thisembodiment of the present invention, SAS 5550 first determines atemporally closest leader-offset-stream by computing distances, forwardand backward, in time from the arrival time of a client's request toview an audio or audio-visual work, to the previous Time-Scale ModifiedLeader-offset-stream start time and the next Time-Scale ModifiedLeader-offset-stream start time, and choosing the smaller of the two asthe temporally closest leader-offset-stream. This can be performed byeither of two methods: (a) by monitoring information output from TSCLStreamer 5210 and TSEL Streamer 5220 or (b) by computing the start timesfor the leaders from information provided by LRBID 5710. In accordancewith this embodiment of the present invention, SAS 5550 then produces,as output, information that directs either TSCL Multicaster 5310 or TSELMulticaster 5320 to add the requesting client to the list ofdestinations for the appropriate Time-Scale Modified Leader offsetstream segments being re-broadcast. SAS 5550 also sends information toMulticaster 5300 and either TSCL Multicaster 5310 or TSEL Multicaster5320 which information conveys client identification and controlinformation and the “intercept-time” for the corresponding Time-ScaleModified Leader offset stream to an offset stream of the original audioor audio-visual work. In response to the intercept information, TSCLMulticaster 5310 and TSEL Multicaster 5320 note the intercept time andschedule the deletion of the requesting client from the list ofmulticast recipients of that TSM Leader offset stream after theintercept time. Additionally, and in response to the interceptinformation, Multicaster 5300 notes the intercept time and schedules theaddition of the requesting client to the list of multicast recipients ofthat offset stream after the intercept time.

As shown in FIG. 12, Time-Scale Expanded Leader Streamer 5220 receives,as input: (a) a code (for example, a number) which represents a desiredLeader Re-broadcast Interval (“LRBI”) from Leader Re-broadcast IntervalDeterminer 5710; (b) a code (for example, a number) which represents adesired number of Time-Division Multiplexed (TDM) channels for theTime-Scale Expanded Leader from Leader Re-broadcast Interval Determiner5710; (c) a code (for example, a number) which represents the durationof the leader being re-broadcast from Leader Re-broadcast IntervalDeterminer 5710 (alternatively, this information could have comedirectly from TSLDD 5600); (d) the start times of the re-broadcastoffset streams of the original audio or audio-visual work from LeaderRe-broadcast Interval Determiner 5710; and (e) data for the audio oraudio-visual work from Storage Device 5100. Time-Scale Expanded LeaderStreamer 5220 produces, as output: (a) the Time-Division Multiplexedcomposite signal of leader segments in a manner similar to thatdescribed above for Work Streamer 4200 (applied as input to TSELMulticaster 5320) and (b) a stream of information giving the playbackposition and time-offset for each time-offset re-broadcast stream of theTime-Scale Expanded Leader (applied as input to SAS 5550).

As shown in FIG. 12, Time-Scale Compressed Leader Streamer 5210receives, as input: (a) a code (for example, a number) which representsa desired Leader Re-broadcast Interval (LRBI) from Leader Re-broadcastInterval Determiner 5710; (b) a code (for example, a number) whichrepresents a desired number of Time-Division Multiplexed (TDM) channelsfor the Time-Scale Compressed Leader from Leader Re-broadcast IntervalDeterminer 5710; (c) a code (for example, a number) which represents theduration of the leader being re-broadcast from Leader Re-broadcastInterval Determiner 5710 (alternatively, this information could havecome directly from TSLDD 5600); (d) the start times of the re-broadcastoffset streams of the original audio or audio-visual work from LeaderRe-broadcast Interval Determiner 5710; and (e) data for the audio oraudio-visual work from Storage Device 5100. Time-Scale Compressed LeaderStreamer 5210 produces, as output: (a) the Time-Division Multiplexedcomposite signal of leader segments in a manner similar to thatdescribed above for Work Streamer 4200 (applied as input to TSCLMulticaster 5310) and (b) a stream of information giving the playbackposition and time-offset for each time-offset re-broadcast stream of theTime-Scale Compressed Leader (applied as input to SAS 5550).

As shown in FIG. 12, Leader Re-broadcast Interval Determiner (LRBID)5710 receives, as input: (a) a code (for example, a number) whichrepresents the duration of the time-scale compressed and time-scaleexpanded leaders from TSLDD 5600; (b) a code (for example, a number)which represents the number of leader re-broadcast offset channelsRe-broadcast Interval Determiner 5700; and (c) a code (for example, anumber) which represents the RBI from RBID 5700. LRBID 5710 produces, asoutput, data which represents the duration of the Leader Re-broadcastInterval (“LRBI”) (applied as input to TSCL Streamer 5210 and TSELStreamer 5220). Leader Re-broadcast Interval Determiner 5710 computesthe LRBI by applying the following formula:LRBI=RBI of audio or audio-visual work/No. of leader re-broadcast offsetchannels   (10)

Note that the greater the number of leader re-broadcast offset channels,the shorter the LRBI, and the less time a requesting client must wait tobegin receiving media data from embodiment 5000.

As shown in FIG. 12, TSCL Multicaster 5310 receives, as input: (a) acomposite signal from TSCL Streamer 5210 and (b) client information (forexample, control and destination) from SAS 5550. Likewise, as shown inFIG. 12, TSEL Multicaster 5320 receives, as input: (a) a compositesignal from TSEL Streamer 5220 and (b) client information (for example,control and destination) from SAS 5550. Then, in accordance with thepresent invention, TSCL Multicaster 5310 and TSEL Multicaster 5320produce, as output, data (for example, message packets) directed towardparticular clients for re-broadcast on a network such as the Internet,WAN, LAN, etc. In accordance with the present invention, TSCLMulticaster 5310 and TSEL Multicaster 5320 each manages a list of allclients that should receive data from particular portions of the TDMcomposite signal in accordance with any one of a number of methods whichare well known to those of ordinary skill in the art. Then, whenever theparticular portion of data in the TDM composite signal is received fromTSCL Streamer 5210 and TSEL Streamer 5220, respectively, TSCLMulticaster 5310 and TSEL Multicaster 5320, respectively, sends theparticular portion of data to all clients (recipients) in the list whoare to receive the particular portion of data (also known asmulticasting). Many methods for broadcasting a portion of data from adata stream (for example, a Time-Division Multiplexed composite signal)to multiple recipients are well known to those of ordinary skill in theart. Control information from SAS 5550 is used in accordance withmethods that are well known to those of ordinary skill in the art tomodify the list of recipients, for example, to add a recipient, or toremove a recipient from the list of destinations when the recipient nolonger desires to receive data from the server. Lastly, whenever thedata stream for a leader merges with a re-broadcast offset stream, theclient is removed from the list of recipients.

Embodiment 5000 has been described in detail above using separatecomponents for ease of understanding the present invention, however, itshould be clear to those of ordinary skill in the art that many of thecomponents perform similar functions to their counterparts in embodiment4000. Further, many of these corresponding components may be combinedwithout loss of functionality. Still further, the intercept intervals inembodiment 5000 of the present invention follow a regular and periodicpattern which advantageously simplifies calculations of slope orplayback rate and can be easily implemented using standard techniquessuch as lookup tables, count-down timers, and the like, all of which arewell known to those of ordinary skill in the art.

Conversely, components of embodiment 5000 may exist in separatelocations connected to one another via a network or any othercommunication means (where the use of the term means is used in thebroadest sense possible).

Although FIG. 12 shows embodiment 5000 to be comprised of separatemodules, in a preferred embodiment, the modules are embodied as softwareprograms or modules which run on a general purpose computer such as, forexample, a personal computer. It should be well known to one of ordinaryskill in the art, in light of the detailed description above, how toimplement these programs or modules in software.

Those skilled in the art will recognize that the foregoing descriptionhas been presented for the sake of illustration and description only. Assuch, it is not intended to be exhaustive or to limit the invention tothe precise form disclosed.

Advantageously, embodiments of the present invention may be used todistribute Movies, Documentaries, or other audio and/or audio-visualworks electronically, such as, for example, pay-per-view programs, videorental and the like. For example, although the distribution wasdescribed using networks, it should be understood that the term networkis used in the broadest sense of the word and includes localdistribution over cable, for example, a hotel distribution system,distribution over satellite, distribution over the public airwaves whereterminals are used in accordance with well known methods to authorizeclient access. It should also be clear that Request Processor 5550 caninclude functionality (in accordance with methods that are well known tothose of ordinary skill in the art) to charge money for receiving workssuch as movies, sporting events and so forth.

For example, those of ordinary skill in the art should readilyunderstand that whenever the term “Internet” is used, the presentinvention also includes use with any non-deterministic delay network. Assuch, embodiments of the present invention include and relate to theworld wide web, the Internet, intranets, local area networks (“LANs”),wide area networks (“WANs”), combinations of these transmission media,equivalents of these transmission media, and so forth.

In addition, it should be clear that embodiments of the presentinvention may be included as parts of search engines used to accessstreaming media such as, for example, audio or audio-visual works overthe Internet.

In further addition, it should be understood that although embodimentsof the present invention were described where the audio or audio-visualworks were applied as input to playback systems, the present inventionis not limited to the use of a playback system. It is within the spiritof the present invention that embodiments of the present inventioninclude embodiments where the playback system is replaced by adistribution system, which distribution system is any device that canreceive digital audio or audio-visual works and re-distribute them toone or more other systems that replay or re-distribute audio oraudio-visual works. In such embodiments, the playback system is replacedby any one of a number of distribution applications and systems whichare well known to those of ordinary skill in the art that furtherdistribute the audio or audio-visual work. It should be understood thatthe devices that ultimately receive the re-distributed data can be“dumb” devices that lack the ability to perform Time-Scale modificationor “smart” devices that can perform Time-Scale Modification.

Although the present invention has been described using Time-ScaleModified Leaders to catch-up or slow-down to a re-broadcast offsetstream of a media work played at a normal playback rate (slope=1), thepresent invention is not thusly limited. For example, furtherembodiments of the present invention can be utilized to enable clientsto merge with time-scale compressed versions of a work (slope>1),time-scale expanded versions of a work (slope<1), or to enable clientsto migrate from a time-scale modified version of a work at oneparticular playback speed to a time-scale modified version of the samework with a different playback speed. In accordance with the presentinvention, this is accomplished by providing transitions from one datastream to another at specific intercept points, or by employingtime-scale modified leaders to transition between versions of a workwith different playback speeds.

In accordance with the present invention, these embodiments arefabricated using embodiment 5000 described above, with a modification toSAS 5550. The modification enables SAS 5550 to compute the temporallyclosest stream with the requested time-scale (i.e., playback-rate)requested by the client at any point during playback.

FIG. 13 shows a graph of location (offset from an origin) in normal andTime-Scale Modified versions of offset re-broadcasts of an audio oraudio-visual work versus time on the horizontal axis. As shown in FIG.13, nine (9) offset data streams are being re-broadcast. Three, (13010,13110, 13210), correspond to re-broadcast of the work with normalplayback rate (slope=1.0); three, (13020, 13120, 13220), correspond tore-broadcast of the work with time-scale compression by a factor of 2(slope=2.0); and three, (13005, 13105, 13205), correspond tore-broadcast of the work with time-scale expansion by a factor of 2(slope=½). As further shown in FIG. 13, at each re-broadcast interval,three (3) stream broadcasts are initiated (compressed, normal, expanded)and that these offset data streams intercept one another at regularintervals where the lines cross (lines intersect when the playbacklocations and playback times are equal). Clients wishing to view orlisten to a work at a different rate can make a seamless transition tothe new rate at points of intersection because the playback locations atthe intersections are identical in each of the streams. As still furthershown in FIG. 13, transition leader 13001 (normal playback rate,slope=1) is shown to demonstrate a transition from playback stream 13005(one-half normal playback rate, slope=½) to playback stream 13020 (twicenormal playback rate, slope=2.0). Additionally, a time-scale modifiedtransition leader 13002 (twice normal playback rate, slope=2.0) is usedto transition from playback stream 13105 (one-half normal playback rate,slope=½) to playback stream 13110 (normal playback rate, slope=1) at atime before the normal intersection with playback stream 13220.Embodiment 5000 can be used to generate the re-broadcasts and thetime-scale modified leaders to enable the client to traversethe-re-broadcast matrix shown in FIG. 13. In that case, client requestswill be received by Request Processor 5500 and transmitted in the mannerdescribed above with respect to the description of embodiment 5000.

For purposes of clarity and ease of understanding the present invention,the foregoing detailed description has used constant time-scalemodification factors, but the present invention is not thusly limitedand includes the use of varying time-scale modification factors usingthe same method and apparatus described above. Thus, Time-ScaleModification may be varied with time without loss of generality. In thiscase, the duration and slope of such a continually varying Time-ScaleModified signal can be computed using any one of a number of formulae,including the following formula:Duration=previous duration+(time-interval*tsm_factor)   (11)

Although for clarity and ease of understanding the previous inventionshave been described broadcasting a single work, it should be clear thatembodiments of the present invention are not thusly limited and theinventive technique can be applied to multiple works existing in asingle embodiment.

Another aspect of the present invention relates to the use of extrainformation broadcast in conjunction with an audio or audio-visual workfrom a server to restrict, or direct, playback rates at the client.Embodiments of this aspect of the present invention can be used in avariety of ways. For example, a public service announcement regardingemergency information, safety information, and the like may be missed ifthe client is listening at a very fast rate (learning impaired andhearing impaired individuals may wish to have important public serviceor emergency broadcasts played at playback rates below the normalplayback rate to aid in comprehension). Since these messages may be ofvital importance, a need exists to restrict the playback rate for theclient in a client-server system that supports Time-Scale Modification,or to notify the client of the importance of these messages.

In accordance with this aspect of the present invention, informationused to restrict, or direct, playback rates at the client may be“in-band” (i.e., occurring within the signal being transmitted, forexample, as a specific frequency tone or data code within a header of adata packet) or “out-of-band” (i.e., occurring within a data packetassociated with, but not comprising, media data).

FIG. 14 shows a block diagram of embodiment 21000 of the presentinvention which transmits information relating to the content and/orappropriate playback speed of media data to clients receiving the mediadata.

As shown in FIG. 14, Streaming Data Source 21100 provides, as output:(a) data representing an audio or audio-visual work through Network21200 (Network 21200 is a network in the broadest sense describedabove), there are many methods which are well known to those of ordinaryskill in the art for fabricating Streaming Data Source 21100, and (b) asignal to TSM Control Source 21150 indicating the transmission of thedata and client identifier information for clients who will haveplayback rates restricted. Note that the components of embodiment 21000may exist in separate locations connected to one another via a networkor any other communication means (where the use of the term means isused in the broadest sense possible).

As further shown in FIG. 14, in response to the signal, TSM ControlSource 21150 transmits playback code data, for example, a code, onNetwork 21200 to all identified clients that will have their playbackrates directed for data received from Streaming Data Source 21100.

Although FIG. 14 shows the transmission of the media data and theplayback code data being transmitted over the same network, the presentinvention is not thusly limited. In fact, the present invention includesembodiments where the media data and playback codes are transmitted overdifferent communications paths. Further, the transmission of theplayback code need not be coordinated with the transmission of the mediadata as described above. The playback code data can be transmitted priorto the transmission of the media data and include information used toenable its coordination with the media data. For example, the playbackcode data may include times (and time intervals) in the media work thatare targeted for use in restricting playback rates.

As still further shown in FIG. 14, Capture Buffer 21400 receives thefollowing, as input: (a) media data input from Network 21200; (b)requests for information about the amount of data stored therein from aCapture Buffer Monitor (not shown, this is optional); and (c) requestsfor media stream data from TSM System 21800. In response, Capture Buffer21400 produces the following, as output: (a) a stream of datarepresenting portions of an audio or audio-visual work (applied as inputto TSM System 21800); (b) a stream of location information used toidentify the position in the stream of data (applied as input to TSMSystem 21800); and (c) an indication of the amount of data storedtherein (applied as input to the optional Capture Buffer Monitor). Itshould be well known to those of ordinary skill in the art that CaptureBuffer 21400 may include a digital storage device. There are manymethods well known to those of ordinary skill in the art for utilizingdigital storage devices such as, for example, a “hard disk drive,” tostore and retrieve general purpose data and there exist manycommercially available apparatus which are well known to those ofordinary skill in the art for use as a digital storage device such as,for example, a CD-ROM, a digital tape, a magnetic disk, and so forth.TSM Control Decoder 21450 receives, as input, playback code data fromNetwork 21200 (as discussed above, it can receive this data from adifferent communication channel as well). TSM Control Decoder 21450produces, as output, playback code data and applies it, as input, to TSMRate Determiner 21700.

As yet still further shown in FIG. 14, TSM Rate Determiner 21700receives the following, as input: (a) a signal (from TSM Control Decoder21450) that represents a playback rate; (b) client generated playbackrate requests (received by a client interaction interface apparatus inaccordance with any one of many methods which are well known to those ofordinary skill in the art (not shown for ease of understanding thepresent invention)); (c) a parameter designated Interval_Size; and (d) aparameter designated Speed_Change_Resolution. In response, TSM RateDeterminer 21700 produces, as output a rate signal representing a TSMrate, or playback rate, which rate signal is applied as input to TSMSystem 21800. TSM Rate Determiner 21700 generally passes clientgenerated rate requests to its output (without modification), therebyenabling the client to control the playback rate. Whenever TSM RateDeterminer 21700 receives information from TSM Control Decoder 21450,TSM Rate Determiner 21700 processes that information to determine anappropriate playback rate to output. For example, TSM Rate Determiner21700 may override the client requested rate request if the informationfrom TSM Control Decoder 21450 specifies that the media work beingreceived is of critical importance to public safety. Additionally, TSMRate Determiner 21700 may process the information from TSM ControlDecoder 21450 according to a rule-set or other algorithm specified bythe client. For example, the rule-set or algorithm can fast-forwardthrough all commercial content in the media work being received, slowdown for specific types of content, using techniques described in U.S.patent application entitled “Method and Apparatus for Generation ofListener Interest Filtered works, which patent application has the sameinventor as the present application and is incorporated by referenceherein.

In a preferred embodiment of the present invention, TSM Rate Determiner21700 uses a parameter Interval_Size to segment the input digital datastream in Capture Buffer 21400 and to determine a single TSM rate foreach segment of the input digital stream. Note, the length of eachsegment is given by the value of the Interval_Size parameter. Further,TSM Rate Determiner 21700 uses a parameter Speed_Change_Resolution todetermine appropriate TSM rates to pass to TSM System 21800. A desiredTSM rate is converted to one of the quantized levels in a manner whichis well known to those of ordinary skill in the art. This means that theTSM rate, or playback rate, can change only if the desired TSM ratechanges by an amount that exceeds the difference between quantizedlevels, i.e., Speed_Change_Resolution. As a practical matter then,parameter Speed_Change_Resolution filters small changes in TSM rate, orplayback rate. The parameters Interval_Size and Speed_Change_Resolutioncan be set as predetermined parameters for embodiment 21000 inaccordance with methods which are well known to those of ordinary skillin the art or they can be entered and/or varied by receiving user inputthrough a user interface in accordance with methods which are well knownto those of ordinary skill in the art. However, the manner in whichthese parameters are set and/or varied are not shown for ease ofunderstanding the present invention.

Embodiments of TSM System 21800 and Playback System 21500 have beendescribed in detail above.

Although FIG. 14 shows embodiment 21000 to be comprised of separatemodules, in a preferred embodiment, the modules are embodied as softwareprograms or modules which run on a general purpose computer such as, forexample, a personal computer. It should be well known to one of ordinaryskill in the art, in light of the detailed description above, how toimplement these programs or modules in software.

Conversely, components of embodiment 21000 may exist in separatelocations connected to one another via a network or any othercommunication means (where the use of the term means is used in thebroadest sense possible).

Advantageously, in accordance with the present invention, theabove-described information used to control the playback speed duringparticular portions of the media work, for example, commercials. Thus, aclient may be prevented from fast forwarding through the commercials.However, in an alternative embodiment, clients may pay for the abilityto automatically fast-forward through all commercial advertisements inan audio or audio-visual work being received. In such an alternativeembodiment, a user interface module (fabricated in accordance with anyone of the many methods which are well known to those ordinary skill inthe art) receives client requests and charge information to effectuatethe functionality.

FIG. 15 shows a block diagram of embodiment 22000 of the presentinvention in which information relating to the playback speed and/orcontent of the media data being broadcast to clients is embedded in themedia work. As shown in FIG. 15, Media Work Source 22100 provides, asoutput, data representing an audio or audio-visual work to Compositer22160 transmits playback code data, for example, a code, to Compositer22160. Compositer 22160 outputs a data signal which is encoded byEncoder 22170 using any number of methods well known to those ofordinary skill in the art and transmitted to Network 22200 (Network22200 is a network in the broadest sense described above) to clients,for example, who have requested the audio or audio visual work.

As further shown in FIG. 15, data from Network 22200 is applied as inputto Decoder 22310 which decodes the encoded data signal using any numberof methods well known to those of ordinary skill in the art. The decodeddata is applied as input to Separator 22320 which separates the playbackcode data from the media data and applies the playback code data asinput to TSM Control Decoder 22450 and the media data as input to TSMSystem 22800. TSM Control Decoder 22450 decodes the playback codeinformation and produces as output a TSM Rate which is applied as inputto TSM Rate Determiner 22700. In accordance with the present invention,TSM Rate Determiner 22700, TSM System 22800 and Playback System 22500are the same as the corresponding components described above withrespect to embodiment 21000. In accordance with this embodiment of thepresent invention, TSM Rate Determiner 22700 uses the TSM Rate from TSMControl Decoder to set the playback rate and override client input.

Although FIG. 15 shows embodiment 22000 to be comprised of separatemodules, in a preferred embodiment, the modules are embodied as softwareprograms or modules which run on a general purpose computer such as, forexample, a personal computer. It should be well known to one of ordinaryskill in the art, in light of the detailed description above, how toimplement these programs or modules in software.

Conversely, components of embodiment 22000 may exist in separatelocations connected to one another via a network or any othercommunication means (where the use of the term means is used in thebroadest sense possible).

Although the detailed description used the terms playback rate and TSMrate, and the terms playback and playback apparatus, these terms shouldbe understood to include any type of presentation rate (i.e., a rate ofpresentation of information) and any type of presentation apparatus. Assuch, these terms are to be understood as being used in the broadestsense. In addition, although the detailed description used the termsmedia, media work, media data, media broadcast, audio or audio-visualwork, and information, these terms should be understood to refer to anytype of information or data. As such, these terms are to be understoodas being used in the broadest sense

1-13. (canceled)
 14. A method for broadcasting information from a serverto a client, comprising: receiving a request at an arrival time from aclient to receive a work; and multicasting data on a network at amulticasting rate in response to: (a) a signal comprised of interleavedsegments of the work, the interleaved segments corresponding to segmentsof the work that are multicast at predetermined starting times and (b)client information that identifies recipients of data for particularportions of the signal.
 15. The method of claim 14, wherein the arrivaltime is different from the predetermined starting times, furthercomprising: determining one of the predetermined starting times that isclose to the arrival time; determining a transmission rate differentfrom the multicasting rate; and transmitting the work at thetransmission rate for the time period, the transmission rate is suchthat a location in the transmitted the work will substantiallysynchronize after the time period with a location in the work multicastat the close predetermined starting time.
 16. The method of claim 15,further comprising: receiving the transmitted work in a buffer at aclient device or server; and playing back the work from the buffer at aplayback rate that prevents the buffer from overflowing.
 17. The methodof claim 15, wherein the transmitting the work further comprisestransmitting the transmission rate.
 18. The method of claim 17, whereinthe transmitting the transmission comprises transmitting thetransmission rate before transmitting the work.
 19. The method of claim15, further comprising: determining that the location in the transmittedwork is substantially the same as the location in the multicast work atthe close predetermined starting time; and multicasting the data to theclient.
 20. The method of claim 15, further comprising: after the timeperiod, multicasting the data to the client.
 21. The method of claim 15,wherein the close predetermined time is prior to the arrival time andthe transmission rate is greater than the multicasting rate.
 22. Themethod of claim 15, wherein the close predetermined time is after thearrival time and the transmission rate is less than the multicastingrate.
 23. A method for displaying a work transmitted to a client device,comprising: receiving the work and displaying the work as it isreceived; receiving a request to stop displaying the work, andthereafter recording the work as it is received; receiving a request todisplay the work; and displaying the work from the recording at anincreased playback rate for a period of time.
 24. The method of claim23, wherein the period of time is a time it takes a location in therecording to synchronize substantially with the work being received. 25.The method of claim 24, further comprising displaying the work as it isreceived.
 26. An apparatus which transmits information from a server toa client, comprising: a request processor that provides client addressinformation; a multicaster that multicasts data on a network at amulticasting rate in response to: (a) a signal comprised of interleavedsegments of the work, the interleaved segments corresponding to segmentsof the work that are multicast at predetermined starting times and (b)the client address information that identifies recipients of data forparticular portions of the signal, the request processor beingconfigured to receive a request for information from a client at anarrival time different from the predetermined starting times; a ratedeterminer that determines one of the predetermined starting times thatis close to the arrival time and a transmission rate different from themulticasting rate; and a variable rate broadcaster that transmits thework at the transmission rate for a time period, the transmission ratebeing such that a location in the transmitted the work willsubstantially synchronize after the time period with a location in thework multicast at the close predetermined starting time.
 27. Theapparatus of claim 26, further comprising a work streamer, responsive tothe work, that generates the signal.
 28. A method for displaying a worktransmitted to a client device, comprising: receiving the work andrecording the work as it is received; receiving a request to display thework while it is being received; and displaying the work from therecording at an increased playback rate for a period of time.
 29. Themethod of claim 28, wherein the period of time is a time it takes alocation in the recording to synchronize substantially with the workbeing received, the method further comprising: displaying the work as itis received after the time period. 30-32. (canceled)
 33. The method ofclaim 15, further comprising: receiving the transmitted work in a bufferat a client device or server; and playing back the work from the bufferat a playback rate that prevents the buffer from underflowing. 34.(canceled)